Hosts of websites sometimes sell or lease space on their websites to content providers. Often, it is useful for the hosts to provide content relevant to the content providers, such as data related to traffic on the website. In particular, the content providers often pay for space on a website based on the number of interactions (mouse clicks or mouseovers) users have with such websites. The data may be related to user clicks, queries, views, or any other type of user interaction with the website. Sometimes, systems that process this data fail or need to be temporarily disabled for maintenance, and data is lost. This can lead to inaccuracies in the reported statistics and can also lead content providers to underpay or overpay the website host. Thus, robust mechanisms are desired for providing reliable aggregate data in a useful form.